Leaving the leaves on the lawn returns the nutrients to the tree & lawn and amends the existing soil to retain more moisture.
Saving the leaves to add to your compost pile will provide carbons for the proper balance in decomposing food and yard waste.
Mow over the leaves weekly until they have reached confetti size. Leaves will "melt" into grass with fall rains & winter snow and it will be gone by spring.
Create a compost area that enhances your neighborhood & landscaping.
Secure from blowing winds. Use the following spring in compost pile.